Student&#39;s drafting instrument



April 5, 1966 F. c. MERRIFIELD STUDENTS DRAFTING INSTRUMENT Filed Feb. 12, 1963 United States Patent 3,243,882 STUDENTS DRAFTING INSTRUMENT Frederick Charles Merrifield, Sanford Ink Co., 2740 Washington Blvd., Bellwood, Ill. Filed Feb. 12, 1963, Ser. No. 257,960 4 Claims. (Cl. 33-93) This invention relates generally to the art of mechanical drawing and more particularly to drafting instruments.

In one specific aspect, the present invention relates to a portable drafting instrument that is adapted for use by student draftsmen, student engineers and the like.

In the past, it has been common practice for students to use a collection of loose drafting implements including triangles, a T-square, protractors, etc. The mere number of separate implements that has been thus required has proved to be a substantial inconvenience, especially in view of the fact that these tools are ordinarily transported between a drafting shop and the students private study room. Appreciable annoyance and frustration can arise upon discovering that one or more implements has been left behind. Moreover, the dexterity needed to manipulate an assemblage of these separate implements has proved a bar to rapid, accurate work. These problems have been solved by professional drafting instruments; but the cost and lock of portability of these latter instruments has prevented their widespread use by students.

Accordingly, a general object of the present invention is to provide a new and improved drafting instrument.

Another object of the invention is to provide a single drafting instrument that is capable of replacing a set of conventional triangles and protractors.

Still another object of the invention is to provide a lightweight, portable and relatively inexpensive drafting instrument.

And still another object of the invention is to provide a drafting instrument that is accurate to use and easy to manipulate.

A further object of the invention is to provide a drafting instrument that is arranged for independent movement of a ruling triangle and a cooperating protractor.

And a yet further object of the invention is to provide a drafting instrument in which friction is employed to hold the setting of a ruling triangle.

These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.

A structure in accordance with the invention includes a base member having a stub arm portion extending generally perpendicularly from a straight edge portion, a triangle member adapted for pivotal connection to the stub arm portion in underlying relationship, a protractor member adapted for pivotal connection to the stub arm portion in overlying relationship, and a coupling unit pivotally connecting the triangle member and the protractor member to the stub arm portion, the coupling unit including means for biasing the triangle member and the protractor member against the stub arm portion for frictionally locking the parts together.

In order that the principles of the invention may be readily understood, a single embodiment thereof, to which the application is not to be restricted, is shown in the accompanying drawing wherein:

FIG. 1 is a top plan view of a drafting instrument constructed in accordance with the principles of the inven tion and viewed as it would be in use, two extreme positions of the ruling triangle being shown respectively in solid outline and in broken outline;

FIG. 2 is an exploded perspective view of the base member, the triangle member and the protractor member of the drafting instrument of FIG. 1;

FIG. 3 is an enlarged view taken substantially along the line 3-3 of FIG. 1; and

FIG. 4 is a view taken substantially along the line 4-4 of FIG. 3.

Referring now in detail to the drawing, specifically to FIG. 1, a drafting instrument indicated generally by the numeral 10 will be seen to include a base member 12, a triangle member 14, a protractor member 16 and a coupling unit 18. The base member 12 includes a straight edge portion 20 and a stub arm portion 22, stub arm portion 22 extending substantially perpendicularly from the straight edge portion 20 adjacent the mid-section thereof. The portion 20 is fashioned with a straight edge 24 that is adapted guidably to contact a T-square or other analogous rail, and the opposite edge of the portion 20 is shaped to define a shoulder or step 26, the stub arm portion 22 being secured to the straight edge portion 20 by being disposed on the step 26 with an adhesive or a fusion joint therebetween. The stub arm portion 22 is thus spaced above the undersurface of portion 20 by the thickness of step 26. Since the undersurface of the straight edge portion 20 is adapted to ride on the drafting work, the stub arm portion 22 is therefore spaced above the drafting work.

The triangle member 14 is adapted for pivotal connection to the stub arm portion 22 in underlying relationship therewith in order that the undersurface of the triangle member 14 may be substantially coplanar with the undersurface of the base member 12, thus establishing a plane for stable and uniform contact between the drafting instrument 10 and the underlying drafting work. In order to achieve the desired pivotal connection, the stub arm portion 22 is fashioned with a circular aperture 28, best seen in FIG. 2; and the triangle member 14 is provided with a circular aperture 30 of similar size for alignment with the circular aperture 28. So that the adjacent edges of the triangle member 14 may be disposed in abutting contact with the outside edge of step 26, the corner of the triangle 14 which is juxtaposed with aperture 30 is rounded to form a heel 32 best seen in FIG. 2. This heel slidably engages the outermost edge of the step 26, permitting free pivotal movement of the triangle member 14 relative to the base member 12 and further accommodating the desired edgewise abutment of the triangle member and the base member.

The triangle member 14 is shown to be a flat, imperforate member having two 45 angle corners and a angle corner, the 90 angle corner containing the aperture 30. However, it is recognized that the triangle member 14 may be perforated with circular or elliptical holes in order to provide a guide for tracing such figures on the drafting work. Moreover, the side of the triangle which defines the hypotenuse may be eliminated, if desired, to reduce the triangle member 14 to a pair of right angularly disposed arms. It is additionally contemplated that the triangle member 14 may be fabricated to possess 30 and 60 angle corners as well as the 45 angle corners which are shown.

Continuing with particular reference to FIG. 2, the protractor member 16 is seen to include a circular aperture 34 which is fashioned to be of a size similar to that of the apertures 28 and 30 and in order that it may be aligned with these latter apertures for use in pivotally connecting the protractor member to the stub arm portion 22 in overlying relationship therewith. The protractor member 16 comprises a sector plate 36, which incorporates the aperture 34, and a segment plate 38 secured to the distal portion of the sector plate in underlying relationship. Suitable means are provided for this attachment such as an adhesive joint or a fusion joint. The segment plate 38 carries a sequence or graduated indicia lines 40 which are arranged to indicate degrees in angular measurement and which radiate from the pivot center defined by coupling unit 18. Advantageously, the indicia lines 40 are combined with numerical indications 42 of the major angular measurements. By afiixing the segment plate 38 to the underside of the sector plate 36, the indicia lines 40 are brought closer to the drafting work, reducing parallax concomitantly thereby.

The triangle member 14 is provided with indicator lines 44, 46 and 48; and these indicator lines radiate from the pivot center defined by the coupling unit 18. The indicator lines 44, 46 and 48 are intended for cooperative use with the indicia lines 40 in establishing a desired relative position of rotation of triangle member 14 and for ease in measuring the angulation of lines on the drafting work. Pursuant to this objective, the triangle member 14 and the protractor member 16 are fabricated of transparent material for visual ease in aligning the indicator lines with lines on the drafting work and in aligning the indicator lines with the indicia lines. Such materials as the methylmethacrylate casting resins and the various polystyrene resins have proved useful for this purpose. The indicia lines 40 and the indicator lines 44, 46 and 48 are advantageously provided by scribing the respective members and subsequently filling the scribed grooves with the paint or other suitable, opaque material. Furthermore, the indicator lines 44 are disposed in right angular relationship to establish datum lines; and the next innermost indicator lines, indicator lines 46, are disposed at 30 relative to the corresponding datum line while the final indicator line, indicator line 48, is usefully situated bisecting the right angular corner of the triangle member 14. Other configurations of the indicator lines may, of course, be employed.

Other datum lines may also be provided such as the lines 50 on the straight edge portion 20 and the stub arm portion 22 of the base member, lines 50 being usefully employed, for example, in locating the stub arm portion at the midline of the straight edge portion.

Turning now to a consideration of FIGS. 3 and 4 for a more detailed description of the coupling unit 18, that unit is seen to include a cylindrical sleeve 52 which passes freely through the aligned apertures 28, 30 and 34 formed respectively in the stub arm portion 22, the triangle member 14 and the sector plate 36. The sleeve 52 is formed as a tubular element, and the lower end is tapped for threadedly receiving a bolt 54, bolt 54 being provided with a broad head 56 that acts as a fixed abutment underlying the triangle member 14. Advantageously, the triangle member 14 is provided with a counterbore opening from its undersurface for receiving the head 56 of bolt 54 in flush relationship.

An annular cup member 58 is slidably disposed on the sleeve 52 overlying the protractor member 16 to define a movable abutment, the cup member 58 desirably contacting a washer 60 which acts as a bearing between the cup member and the protractor member. At its upper end, the sleeve member 52 is fashioned with a radially extending head 62, and a compression spring 64 is located between the cup member 58 and the head 62 to bias the cup member generally toward the head 56 of bolt 54, thus frictionally locking both the triangle member 14 and the protractor member 16 to the stub arm portion 22. The spring 64 is selected to be soft enough to permit independent movement of the protractor member and the triangle member.

In compliance with a feature of the invention the cou pling unit 18 is arranged to relieve at least some of the bias provided by spring 64 whereby to ease independent manipulation of the protractor member and the triangle member. For this purpose, equally arcuately disposed spring fingers 66 or reversibly situatable regulating means are passed through appropriately positioned, radial openings in the sleeve 52, the butt ends of the fingers 66 engaging the cup member 58 and the tip ends of the fingers 66 engaging the nose of a plunger 68.. The plunger 68 rides in the upper, smooth bore of sleeve 52 and includes an operating stern portion 70 that extends through a hole 72 formed centrally in the head 62. Advantageously, the hole 72 is of smaller diameter than the smooth bore of the sleeve 52 whereby to provide a shoulder abutment limiting the upward travel of the plunger 68. The reversibly situatable regulating means contacts the movable abutment and is manipulatable between two extreme positions of adjustment. This regulating means urges the movable abutment toward the fixed abutment to frictionally lock the triangle and the protractor to the arm portion; and the regulating means frees the triangle and the protractor at least partially from the positions of frictional locking in a reversed position of relative adjustment.

As will be recognized, the application of downwardly directed force on the stem portion of plunger 68 will cause the nose thereof to engage the spring fingers 66, the fingers 66 thereupon acting as resilient levers fulcrumed in their respective apertures in the sleeve 52. So actuated, the fingers 66 tend to raise the cup member 58 relative to the sleeve 52 and toward the head 62 thereby compressing the spring 64 and releasing the protractor member 16 and the triangle member 14 to relatively free movement.

The operation and use of the drafting instrument 10 will be apparent from the foregoing descriptions. It will also be apparent that the disclosed drafting instrument is readily portable, uncomplicated and lightweight in nature.

The specific example herein shown and described is to be considered as being primarily illustrative. Various changes in structure and arrangement will, no doubt, occur to those skilled in the art, and such changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A portable drafting instrument comprising: a base member having a straight edge portion adapted guidably to contact a T-square or analogous rail and an arm portion extending generally perpendicularly from the straight edge portion spaced above the drafting work; a triangle member adapted for pivotal connection to said arm portion in underlying relationship; a protractor member adapted for pivotal connection to said arm portion in overlying relationship and having graduated indicia lines for use in determining the relative angulation of said triangle member; and a coupling unit pivotally connecting said triangle member and said protractor member to said arm portion, including a cylindrical element passing slidably and rotatably through aligned apertures in said triangle, said arm portion and said protactor member, a fixed abutment on one end of said cylindrical element generally underlying said members, a movable abutment on the opposite end of said cylindrical element generally overlying said members, and reversibly situatable regulating means contacting said movable abutment and being manipulatable between two positions of relative adjustment, said regulating means acting to urge said movable abutment toward said fixed abutment in one position of relative adjustment for frictionally locking said triangle member and said protractor member to said arm portion, said regulating means serving to free said triangle member and said protractor member at least partially from said frictional locking in a different position of relative adjustment.

2. A drafting instrument according to claim 1 wherein said triangle member includes means defining indicator lines radiating from the pivot axis established by said cylindrical element and wherein said base member, said triangle member and said protractor member are of transparent material whereby to facilitate alignment of said indicator lines with lines on said drafting work.

3. A portable drafting instrument comprising: a base member having a straight edge portion adapted guidably to contact a T-square or analogous rail and an arm portion extending generally perpendicularly from the straight edge portion spaced above the drafting Work; a triangle member adapted for pivotal connection to said arm portion in underlying relationship; a protractor member adapted for pivotal connection to said arm portion in overlying relationship and having graduated indicia lines for use in determining the relative angulation of said triangle member; and a coupling unit pivotally connecting said triangle member and said protractor member to said arm portion,' including a cylindrical element passing slidably and rotatably through aligned apertures in said triangle, said arm portion and said protractor member, a fixed abutment on one end of said cylindrical element generally underlying said members, a movable abutment on the opposite end of said cylindrical element generally overlying said members, means acting between said cylindrical element and said movable abutment to bias said movable abutment toward said fixed abutment for frictionally locking said triangle member and said protractor member to said arm portion, and means operative to relieve at least some of the bias whereby to ease independent manipulation of said protractor member and said triangle member, said last mentioned means comprising a plunger element slidably received in said cylindrical element, a lever member fulcrumed on said cylindrical element and engageable at its opposite ends with said plunger element and said movable abutment respectively, whereby movement of said plunger element into aggressive contact with said lever member acts to lift said movable abutment against said bias means to counteract at least a portion of the force of said bias means.

4. A drafting instrument according to claim 3 wherein said bias means is a compression spring.

References Cited by the Examiner UNITED STATES PATENTS 523,733 7/1894 Sanderson 33-93 795,145 7/1905 Loomis 33-93 2,641,843 6/1953 Hart et a1 33-102 X FOREIGN PATENTS 934,966 1/1948 France.

ISAAC LISANN, Primary Examiner. 

1. A PORTABLE DRAFTING INSTRUMENT COMPRISING: A BASE MEMBER HAVING A STRAIGHT EDGE PORTION ADAPTED GUIDABLY TO CONTACT A T-SQUARE OR ANALOGOUS RAIL AND AN ARM PORTION EXTENDING GENERALLY PERPENDICULARY FROM THE STRAIGHT EDGE PORTION SPACED ABOVE THE DRIFTING WORK; A TRIANGLE MEMBER ADAPTED FOR PIVOTAL CONNECTION TO SAID ARM PORTION IN UNDERLYING CONNECTION TO SAID ARM PORTION IN ADAPTED FOR PIVOTAL CONNECTION TO SAID ARM PORTION IN OVERLYING RELATIONSHIP AND HAVING GRADUATED INDICIA LINES FOR USE IN DETERMINING THE RELATIVE ANGULATION OF SAID TRIANGLE MEMBER; AND A COUPLING UNIT PIVOTALLY CONNECTING SAID TRIANGLE MEMBER AND SAID PROTRACTOR MEMBER TO SAID ARM PORTION, INCLUDING A CYLINDRICAL ELEMENT PASSING SLIDABLY AND ROTATABLY THROUGH ALIGNED APERTURES IN SAID TRIANGLE, SAID ARM PORTION AND SAID PROTACTOR MEMBER, A FIXED ABUTMENT ON ONE END OF SAID CYLINDRICAL ELEMENT GENERALLY UNDERLYING SAID MEMBERS, A MOVABLE ABUTMENT ON THE OPPOSITE END OF SAID CYLINDRICAL ELEMENT GENERALLY OVERLYING SAID MEMBERS, AND REVERSIBLY SITUATABLE REGULATING MEANS CONTACTING SAID MOVABLE ABUTMENT AND BEING MANIPULATABLE BETWEEN TWO PORTIONS OF RELATIVE ADJUSTMENT, SAID REGULATING MEANS ACTING TO URGE SAID MOVABLE ABUTMENT TOWARD SAID FIXED ABUTMENT IN ONE POSITION OF RELATIVE ADJUSTMENT FOR FRICTIONALLY LOCKING SAID TRIANGLE MEMBER AND SAID PROTRACTOR MEMBER TO SAID ARM PORTION, SAID REGULATING MEANS SERVING TO FREE SAID TRIANGLE MEMBER AND SAID PROTRACTOR MEMBER AT LEAST PARTIALLY FROM SAID FRICTIONAL LOCKING IN A DIFFERENT POSITION OF RELATIVE ADJUSTMENT. 